ASTM D3686-95(2001)e1
(Practice)Standard Practice for Sampling Atmospheres to Collect Organic Compound Vapors (Activated Charcoal Tube Adsorption Method)
Standard Practice for Sampling Atmospheres to Collect Organic Compound Vapors (Activated Charcoal Tube Adsorption Method)
SIGNIFICANCE AND USE
Promulgations by the Federal Occupational Safety and Health Administration (OSHA) in 29 CFR 1910.1000 designate that certain organic compounds must not be present in workplace atmospheres at concentrations above specific values.
This practice, when used in conjunction with Practice D 3687, will provide the needed accuracy and precision in the determination of airborne time-weighted average concentrations of many of the organic chemicals given in 29 CFR 1910.1000, CDC-99-74-45 and HSM-99-71-31.
A partial list of chemicals for which this method is applicable is given in Annex A1, along with their OSHA permissible exposure limits.
FIG. 1 Activated Charcoal Adsorption Sampling Tube
SCOPE
1.1 This practice covers a method for the sampling of atmospheres for determining the presence of certain organic vapors by means of adsorption on activated charcoal using a charcoal tube and a small portable sampling pump worn by a worker. A list of some of the organic chemical vapors that can be sampled by this practice is provided in Annex 1. This list is presented as a guide and should not be considered as absolute or complete.
1.2 This practice does not cover any method of sampling that requires special impregnation of activated charcoal or other adsorption media.
1.3 The values stated in SI units are to be regarded as the standard.
1.4 This standard does not purport to address all of the safety concerns, if any, associated with its use. It is the responsibility of the user of this standard to establish appropriate safety and health practices and determine the applicability of regulatory limitations prior to use. A specific safety precaution is given in .
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Designation:D3686–95 (Reapproved 2001)
Standard Practice for
Sampling Atmospheres to Collect Organic Compound
Vapors (Activated Charcoal Tube Adsorption Method)
This standard is issued under the fixed designation D 3686; the number immediately following the designation indicates the year of
original adoption or, in the case of revision, the year of last revision. A number in parentheses indicates the year of last reapproval. A
superscript epsilon (e) indicates an editorial change since the last revision or reapproval.
e NOTE—SI statement was added and part of Footnote F of Table A1.1 was deleted editorially in October 2001.
1. Scope Tubes; Final Report
2.3 OSHA Standard:
1.1 This practice covers a method for the sampling of
CFR 1910 General Industrial OSHA Safety and Health
atmospheres for determining the presence of certain organic
Standard
vapors by means of adsorption on activated charcoal using a
charcoal tube and a small portable sampling pump worn by a
3. Terminology
worker.Alist of some of the organic chemical vapors that can
3.1 For definitions of terms used in this method, refer to
be sampled by this practice is provided in Annex A1. This list
Terminology D 1356.
is presented as a guide and should not be considered as
3.2 Activated charcoal refers to properly conditioned
absolute or complete.
coconut-shell charcoal.
1.2 This practice does not cover any method of sampling
that requires special impregnation of activated charcoal or
4. Summary of Practice
other adsorption media.
4.1 Air samples are collected for organic vapor analysis by
1.3 The values stated in SI units are to be regarded as the
aspirating air at a known rate through sampling tubes contain-
standard.
ing activated charcoal, which adsorbs the vapors.
1.4 This standard does not purport to address all of the
4.2 Instructions are given to enable the laboratory personnel
safety concerns, if any, associated with its use. It is the
to assemble charcoal tubes suitable for sampling purposes.
responsibility of the user of this standard to establish appro-
4.3 Instructions are given for calibration of the low flow-
priate safety and health practices and determine the applica-
rate sampling pumps required in this practice.
bility of regulatory limitations prior to use. A specific safety
4.4 Information on the correct use of sampling devices is
precaution is given in 9.4.
presented.
2. Referenced Documents 4.5 Practice D 3687 describes a practice for the analysis of
these samples.
2.1 ASTM Standards:
D 1356 Terminology Relating to Sampling and Analysis of
5. Significance and Use
Atmospheres
5.1 Promulgations by the Federal Occupational Safety and
D 3687 Practice forAnalysis of Organic Compound Vapors
Health Administration (OSHA) in 29 CFR 1910.1000 desig-
Collected by the Activated Charcoal Tube Adsorption
nate that certain organic compounds must not be present in
Method
workplace atmospheres at concentrations above specific val-
2.2 NIOSH Standard:
3 ues.
CDC-99-74-45 Documentation of NIOSH Validation Tests
5.2 This practice, when used in conjunction with Practice
HSM-99-71-31 Personnel Sampler Pump for Charcoal
D 3687, will provide the needed accuracy and precision in the
determination of airborne time-weighted average concentra-
1 tions of many of the organic chemicals given in 29
This practice is under the jurisdiction ofASTM Committee D22 onAir Quality
andisthedirectresponsibilityofSubcommitteeD22.04onWorkplaceAtmospheres. CFR 1910.1000, CDC-99-74-45 and HSM-99-71-31.
Current edition approved January 15, 1995. Published March 1995. Originally
published as D 3686 – 78. Last previous edition D 3686 – 89.
Annual Book of ASTM Standards, Vol 11.03.
3 4
Available from the U.S. Department of Commerce, National Technical Infor- Available from Superintendent of Documents, U.S. Government Printing
mation Service, Port Royal Road, Springfield, VA 22161. Office, Washington, DC 20402.
Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959, United States.
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D3686–95 (2001)
FIG. 1 Activated Charcoal Adsorption Sampling Tube
5.3 A partial list of chemicals for which this method is penetrate the front section and serves as a warning that
applicable is given in Annex A1, along with their OSHA breakthrough may have occurred. (Annex A1 gives recom-
permissible exposure limits. mended maximum tube loading information for many chemi-
cals.)
6. Interferences
7.1.2.1 Should analysis of the back portion show it to
6.1 Water mist and vapor can interfere with the collection of
contain more than 10 % of the amount found in the front
organic compound vapors. Humidity greater than 60 % can
section,thepossibilityexiststhatsolventvaporpenetratedboth
reduce the adsorptive capacity of activated charcoal to 50 %
sections of charcoal, and the sample must be considered
for some chemicals (1). Presence of condensed water droplets
suspect. These percentages apply to 100/50-mg tubes. For
in the sample tube will indicate a suspect sample.
othersizetubeshavingdisproportionateamountsofcharcoalin
the front and back sections, the percentages used to indicate
7. Apparatus
potential breakthrough must be adjusted to take into account
7.1 Charcoal Tube: different ratios of charcoal. If results from the analysis of
7.1.1 A sampling tube consists of a length of glass tubing
suspect samples are used to calculate vapor concentrations, the
containing two sections of activated charcoal which are held in results must be reported as equal to or greater than the
place by nonadsorbent material and sealed at each end.
calculated concentrations. In such cases, the test must be
7.1.1.1 Sampling tubes are commercially available. The repeated for confirmation of vapor concentration.
tubes range in size from 100/50 to 800/400 mg, which means
NOTE 2—Reportings from suspect samples would have significance
the tubes are divided into two sections with the front section
when health standards are clearly exceeded and the amount by which they
containing 100 to 800 mg of activated charcoal and the back
are exceeded is academic. (See 9.5.)
section containing 50 to 400 mg of activated charcoal. The
7.1.3 The adsorptive capacity and desorption efficiency of
100/50-mg tube ((2-4) and Fig. 1) which is the one most
different batches of activated charcoal may vary. Commercial
frequently used, consists of a glass tube, 70-mm long, 6-mm
tubes, if used, should be purchased from the same batch and in
outside diameter, 4-mm inside diameter, and contains two
sufficient number to provide sampling capacity for a definite
sections of 20/40 mesh-activated charcoal but separated by a
period of time. Care must be taken to have enough tubes from
2-mm section of urethane foam.The front section of 100 mg is
the same batch for a given study.
retained by a plug of glass wool, and the back section of 50 mg
7.1.3.1 Thedesorptionefficiencyandcontaminationlevelof
is retained by either a second 2-mm portion of urethane foam
a batch of tubes should be determined, following the procedure
or a plug of glass wool. Both ends of the tube are flame-sealed.
outlined in Practice D 3687 for activated charcoal. A random
NOTE 1—Urethane foam is known to adsorb certain pesticides (5), for
selection of at least five charcoal tubes from a specified lot
which this practice is contraindicated.
should be taken for these checks.
7.1.1.2 When it is desirable to sample highly volatile
7.1.4 Pressure drop across the sampling tube should be less
compoundsforextendedperiods,oratahighvolumeflowrate,
than 25 mm Hg (3.3 kPa) at a flow rate of 1000 mL/min and
a larger device capable of efficient collection can be used,
less than 4.6 mm Hg (0.61 kPa) at a flow rate of 200 mL/min.
provided the proportions of the tube and its charcoal contents
7.1.5 Charcoal sampling tubes prepared in accordance with
are scaled similarly to the base dimensions, to provide nomi-
this practice and with sealed glass ends may be stored
nally the same linear flow rate and contact time with the
indefinitely.
charcoal bed.
7.2 Sampling Pumps:
7.1.2 The back portion of the sampler tube, which may
7.2.1 Any pump whose flow rate can be accurately deter-
contain between 25 and 100 % of the mass of activated
mined and be set at the desired sampling rate is suitable.
charcoal present in the front section, adsorbs vapors that
Primarily though, this practice is intended for use with small
personal sampling pumps.
7.2.2 Pumps having stable low flow rates (10 to 200
The boldface numbers in parentheses refer to the list of references at the end of
this standard. mL/min) are preferable for long period sampling (up to 8 h) or
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D3686–95 (2001)
when the concentration of organic vapors is expected to be
Minimum sample volume, m (1)
high. Reduced sample volumes will prevent exceeding the
minimum detection limit, mg
adsorptivecapacityofthecharcoaltubes.(Suggestedflowrates
0.2 3 permissible exposure limit, mg/m
and sampling times are given in Annex A1 for anticipated
Maximum sample volume, m (2)
concentration ranges. Sample volumes are also discussed in
9.5.) tube capacity for vapors, mg
7.2.3 Pumps are available that will provide stable flow rates 2 3 permissible exposure limit, mg/m
between 6 5 %. Pumps should be calibrated before and after
9.5.2 Select a sampling rate that, in the sampling time
sampling. If possible, flow rates should be checked during the
desired, will result in a sample volume between the minimum
course of the sampling procedure.
and maximum calculated in 9.5.1.
7.2.4 All sampling pumps must be carefully calibrated with
9.5.2.1 Generally a long sampling time at a low flow rate is
the charcoal tube device in the proper sampling position. (See
preferable to short-term high-volume sampling. This is consis-
Annex A2 for calibration procedure.)
tent with the fact that most health standards are based on
8-h/day time-weighted averages of exposure concentrations.
8. Reagents
9.5.2.2 Asampleflowrateoflessthan10mL/min,however,
8.1 Activated Coconut-Shell Charcoal—Prior to being used should not be used. Calculations based upon diffusion coeffi-
to make sampling devices the charcoal should be heated in an cients for several representative compounds indicate that
inert gas to 600°C and held there for 1 h. Commercially sampling at less than 10 mL/min may not give accurate
available coconut charcoal (20/40 mesh) has been found to results.
haveadequateadsorptioncapacity.Othercharcoalscanbeused 9.5.2.3 Approximate sample volumes and sample times are
for special applications.
given in Annex A1.
9.5.3 When spot checks are being made of an environment,
9. Sampling with Activated Charcoal Samplers a sample volume of 10 L is adequate for determining vapor
concentrations in accordance with exposure guidelines.
9.1 CalibrationoftheSamplingSystem—Calibrate the sam-
9.6 At the end of the sampling period recheck the flow rate,
pling system, including pump, flow regulator, tubing to be
turn off the pump, and record all pertinent information: time,
used, and a representative charcoal tube (or an equivalent
register reading, and if pertinent, temperature, barometric
induced resistance) with a primary or calibrated secondary
pressure, and relative humidity.
flow-rate standard to 6 5%.
9.6.1 Seal the charcoal tube with the plastic caps provided.
9.1.1 Aprimarystandardpracticeisgivenforthecalibration
9.6.2 Label the tube with the appropriate information to
of low flow-rate pumps in Annex A2 and Fig. A2.1.
identify it.
9.2 Break open both ends of the charcoal tube to be used for
9.7 At least one charcoal sampling tube should be presented
sampling, ensuring that each opening is at least one half the
for analysis as a field blank with every 10 or 15 samples, or for
inside diameter of the tube.
each specific inspection or field study.
9.3 Insert the charcoal tube into the sampling line, placing
9.7.1 Break the sealed ends off the tube and cap it with the
the back-up section nearest to the pump. At no time should
plastic caps. Do not draw air through the tube, but in all other
there be any tubing ahead of the sampling tubes.
ways treat it as an air sample.
9.4 For a breathing zone sample, fasten the sampling pump
9.7.2 The purpose of the field blank is to assure that if the
to the worker, and attach the sampling tube as close to the
sampling tubes adsorb vapors extraneous to the sampling
worker’s breathing zone as possible. Position the tube in a
atmosphere, the presence of the contaminant will be detected.
vertical position to avoid channeling of air through the ad-
9.7.3 Results from the field blanks shall not be used to
sorber sections.
correct sample results. If a field blank shows contamination,
NOTE 3—Warning: Assure that the presence of the sampling equip-
the samples taken during the test must be assumed to be
ment is not a safety hazard to the worker.
contaminated.
9.8 Calculation of Sample Volume:
9.4.1 Turn on the pump and adjust the flow rate to the
9.8.1 For sample pumps with flow-rate meters:
recommended sampling rate.
9.4.2 Record the flow rate and starting time or, depending P T
1 2
Sample volume, mL 5 f 3 t 3 (3)
SΠD
on the make of pump used, the register reading. P T
2 1
9.5 Sampling Volumes—The minimum sample volume will
where:
be governed by the detection limit of the analytical method,
f = flow rate sampled, mL/min,
and the maximum sample volume will be determined by either
t = sample time, min,
the adsorptive capacity of the charcoal or limitations of the
P = pressureduringcalibrationofsamplingpump(mmHg
pump battery.
or kPa)
9.5.1 Onemethodofcalculatingrequiredsamplevolumesis
to determine first the concentration range, over which it is
important to report an exact number, for example from 0.2 to
2 times the permissible exposure concentration, and then
Heitbrink, W. A., “Diffusion Effects Under Low Flow Conditions,” American
calculate the sample volumes as follows: Industrial Hygiene Association Journal, Vol 44, No. 6, 1983, pp. 453–462.
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D3686–95 (2001)
10.1.1 Samples should be capped securely and identified
P = pressure of air sampled (mm Hg or kPa)
clearly.
T = temperature during calibration of sampling pump (K),
10.1.2 Samples collected in charcoal tubes should not be
and
T = temperature of air sampled (K).
kept in warm places or exposed to direct sunlight.
9.8.2 For sample pumps with counters:
10.1.3 Samplesofhighlyvaporousorlow-boilingmaterials,
such as vinyl chloride, should be stored and transported in dry
~R 2 R ! 3 V P 298
2 1 1
V 5 3 3 (4)
ice.
I 760 T 1 273
10.1.4 At present there are no published test data on the
where:
effect of conditions in aircraft cargo holds on capped samples.
R = final counter reading
...
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